Resistor



H. PENDER Dec. 8, 1936.

RESISTOR Filed June 1, 1932 INVENTOR flarolal Fender ATTORNEYS PatentedDec. 8, 1936 UNITED STATES PATENT OFFICE national tance Company,Philadelphia,

Pa.,a corporation of Delaware Application June 1, 1932, Serial No.614,679

5 Claim.

This invention relates to the construction of electrical resistancedevices and, with regard to certain of its more specific features, toresistors for radio apparatus.

One object of the invention is to provide a resistor for radio usehaving a high power rating. Another object of the invention is toprovide a construction for electrical resistance devices which isimpervious to moisture. Another object of the invention is to provide athoroughly insulated resistor. tion is to provide a resistor havingexcellent heat dissipating qualities. Another object of the invention isto provide a device of the above nature which is simple in construction,durable and inexpensive to manufacture.

Other objects will be in part obvious and in part pointed outhereinafter.

The invention accordingly consists in the features offconstruction,combinations of elements, and arrangements of parts as will beexemplifled in the structure to be hereinafter defined and the scope ofthe application of which will be indicated in the following claims.

In the accompanying drawing, in which are shown three of the variouspossible embodiments of the mechanical features of this invention,

Figure 1 is a side elevation of a resistance device constructed inaccordance with the invention;

Figure 2 is a sectional view taken on the line 2-4 of Figure 1;

Figure 3 is a perspective view of a plug;

Figure 4 is a longitudinal sectional view similar to Figure 2 showing amodified form of resistance device;

' Figure 5 is a longitudinal sectional view showing a furthermodification; and

Figure 6 is a cross-sectional view taken on the .or tube II preferablyconstitutes an insulator for .high frequency and for high voltagecharges and nevertheless is preferably composed of a mate rial havingrelatively high heat conductivity. Preferably also it is impervious toair and particularly to moisture in any form, and preferably it isstrong and durable. Although there are several substances fulfilling oneor more of the above requirements which I might use, I prefer Anotherobject of the invento employ for the insulator ID a ceramic such asunglazed porcelain or a substance of the nature of porcelain. The rodIIl may be generally cylindrical, or it may be prismatic, or it may havesuch intimate contact with the wall thereof as to leave substantially noair space surrounding it, is the resistance element I2. Preferably thisresistance element I2 constitutes a glass rod or fiber coated withcarbonaceous substance, such 'as the resistance element disclosed in myprior U. S. Letters Patent #1,832,419 granted November 17, 1931. Such aresistance element is to a high degree flexible, and has a coating ofresistance material hard and firm enough to withstand the operation offorcing the rod into the capillary passage II without scrapingofl. orinjuring in any way the coating. Preferably the capillary passage I l'is circular in cross-section because the resistance material I2 may bemore readily and accurately made of a cylindrical rod or fiber.

Referring to Figures 1 and 2, in a side wall of the rod or tube and nearthe ends thereof 1 form a pair of bores I3, I3. These bores intersectthe capillary passage I I and the resistance element I2 extends into andpreferably through each of these bores I3, I3.

Referring now to Figure 3, I provide a plurality of metal plugs lladapted to m m the bores n,

I3. Each plug is generally cylindrical in form and has formed therein aslot II at one end of a. size to straddle the resistance element It.

Preferablythe plugs are made of metal alloy of such a nature that,uponsolidification from a molten state, it will expand to such an extent asto press firmly against the walls of the bores I3 and be compressedagainst the resistance element I2 without, however, fracturing theinsulating -rod or tube I8 or \the resistance element II, as-

suming the resistance element to comprise a coated glass rod or filamentas described.

Preferably, also the alloy should be of such a nature that it will meltat a temperature low enough to facilitate the manufacture of thearticles in quantity production without danger, however, of fusing inoperation. The alloy also should have good flowing properties so as toconform to the minute irregularities of the ceramic or the like. Theingredients of an alloy having the above mentioned qualities in a markeddegree, which is an example merely of a. preferred alloy, are asfollows:-

- Per cent Antimony 9 to 15 Tin -Q 4 to 6 Lead 87 to 79 Other advantagesof the above and similar alloys are that they will not burn theresistance coating of the resistance material I2, and they have a lowcoefiicient of expansion while in a solid state, comparatively close tothat of glass.

I now place a plug I4 in each of the bores I3 so as to locate theresistance element I2 in the slots I5. I now heat the entire article toa sufficient temperature to melt the plugs I4, and the metal then flowsaround the resistance element I2 and fills the bores I3, I3. Theadvantages of proceeding in this manner are that the metal is able toreach all parts of the bore readily, and as the ceramic is at the sametemperature or an even higher temperature than the metal there is nosudden cooling on contact such as results from attempting to pour moltenmetal. I have found that for the filling of small bores this method ofmolding metal secures a more perfect casting.

While the metal is molten, I introduce into the bores I3, I3 terminalwires IE, IS. Such terminal wires are bendable and may desirably be ofcopper coated with tin which, having little resiliency, will assume anydesired shape. Such wires are excellent conductors of electricity andhave a strong affinity for alloys of the character indicated. Desirablythe ends of the wires I6 that are introduced into the bores I3 areknurled or crimped as shown at I! so that a firm union between the wiresand the solidified metal may resuit.

In the manufacture of resistors as above described I have found itadvantageous to clamp or otherwise secure the bodies I0 upon a conveyorleading into or over a furnace, and an operator may insert the terminalwires I6 when the plugs I4 have melted; the conveyor then carries there-' sistors beyond the heating locus and the metal quickly solidifies,whereupon the resistors may be removed or may automatically be depositedin a box or the like.

The metal alloy, upon solidifying, expands against the walls of thebores I3, I3 and becomes firmly attached to the rod or tube I0 and iscompressed against the resistance element I2. The

electrical connection between the resistance ele,

ment I2 and the terminals I6, I6 is found to be substantially noiselessin an audio circuit.

After the alloy has solidified in the bores I 3, I3 (and either beforeor after the resistors have been taken from the conveyor) moisture-proofinsulating material is introduced upon the top of the metal filling theremainder of the bores, as the amount of metal used is preferably lessthan enough to fill the bores I3, I3. As examples of such moisture-proofinsulating material I have obtained good results by using rosin, orCanada balsam. Such substance forms insulating portions I8, I8, anddesirably also is introduced into the ends of the capillary passage IIforming insulating portions I 9, I 9. When either rosin or Canada balsamis used, it is found that the insulating material penetrates bycapillary attraction or like force into the minute spaces between thenow solidified metal portions I4, I4 and the wall and bottom of thebores I3, and effectually prevents moisture from reaching the resistanceelement I2 and also acts as a cement to further increase the adherenceof the metal I4, I4 to the ceramic I0.

Referring now to Figure 4, a modification of the invention is shown inwhich molded metal portions 20, 20 are introduced into recesses 2|, 2|formed in opposite ends of the insulator Ina. These molded metalportions 20, 20 may be and preferably are of the alloy above indicatedor having similarcharacteristics, As the recesses 2|, 2| are somewhatlarger than the bores I3, I3 I may introduce the metal into the recessesin liquid form, although the method of using a plug and melting it inposition may also be adopted. Extending into each recess 2I is a lateralbore 22 through the cylindrical wall of the ceramic Inc, and throughwhich lateral bore extends a terminal I 5a the inner end of which,embedded in molded metal 20, may be of question-mark shape as shown inFigure 6 to make a firm union between the terminal and the molded metal2!]. Covering the ends of the metal 20 are layers of moistureproofinsulating material 23, 23, desirably Canada balsam or rosin, which actsto firmly cement the met-a1 20 to the ceramic Illa and keeps moisturefrom the resistance element I2 as already described. Desirably a drop ofthis insulating material is placed on the outside of the lateral bores22 sealing any space between them and the wires I 5a, I 5a.

Referring now to Figure 5, a further modification is shown in whichterminal wires I5b, preferably of the shape shown in Figure 5, areintroduced directly into recesses 24 so as to project from opposite endsof the unit. The recesses 24, 24 may be undercut as indicated and any ofthe methods of introducing the molded metal 25, 25 already described, orany other suitable method, may be adopted. Preferably the unit shown inFigure 5 is also sealed against entrance of moisture by means ofmoisture-proof insulating coatings 26. By reason of the undercutportions of the recesses 24, and by reason of the shape of the terminalsI5b, this unit has great strength.

The resistance devices herein described are thoroughly insulated both onsides and ends so that several resistors may be placed in close contactwith each other in the apparatus in which they are used. Furthermore,they are small, light and extremely durable. I'he resistance coating ofthe resistance element I2 is in intimate contact with the substance ofthe insulator thus dissipating heat materially increasing the powercapacity of the device. Porcelain and similar substances are goodconductors of heat and give the resistors a high power rating. Byuniting the terminals I5 to the resistance element with molded or castmetal within the insulator ID a device having a ,small maximum diameteris obtained and thus space, which is at a premium in a radio set, isconserved. Furthermore, except for the terminals I5, there are noexposed conductive parts, and after soldering the terminals to whateverthey are to be connected to in the radio apparatus, the surplus lengththereof may be cut off with a pair of pliers. The resistors of thepresent invention are particularly adapted for mounting in gangformation.

It will thus be seen that there has been provided by this invention anarticle in which the various objects hereinabove set forth, togetherwith many thoroughly practical advantages, are successfully achieved. 1

As many possible embodiments may be made of the above invention and asmany changes might be made in the embodiment above set forth, it is tobe understood that all matter hereinbefore set forth or shown in theaccompanying drawing is to be interpreted as illust'rative and not in alimiting sense.

In the following claims the term molded" is to be construed as meaningcast, liquefied in position, formed by dropping liquid upon something,orspraying with atomized substance, as the term does not in realityrelate to any particular process (as used herein) but is indicative of aparticular condition of metal or other substance, for from thestandpoint of audio-frequency apparatus a connection made in one of theabove indicated manners or in any similarmanner is, in the sense of anarticle of manufacture, difierent from a mere mechanical union, inintimacy of contact and molecular condition of the parts, and solikewise is a seal or covering for insulating or keeping out moisture.

I claim:

1. In a device of the class described, a glass rod filamentary indiameter, a coating of carbonaceous resistance material on thecylindrical surface of said rod but not on the ends thereof, a rightcylinder of insulating material enclosing said rod and said carbonaceoussubstance, the cylinder being slightly longer than the rod and the rodand the cylinder being coaxial there being a passage in the cylinderjust large enough to conveniently hold the rod, bendable metal wiresextending axially from opposite ends of the cylinder said wiresconstituting the only break in the insulation of said device, andadditional more readily conductive material directly contacting the endsof the rod and the carbonaceous substance thereon and also contactingthe wires and holding them in place.

2. In a-device of the class described, in combination, a tubular memberformed from insulating material, said tubular member having recesses inits opposite ends, the dimensions or said recesses being greater atpoints spaced irom the ends of said tubular member, a resistor roddisposed within the bore of said member and having its end portionsdisposed within said recesses, metal in said recesses surrounding andembracing said end portions of said resistor rod and engaging the walls0! said recesses at said points, and wire terminals embedded in themetal or each 01' said recesses.

3. In a device of the class described, in combination, a tubular memberformed from insulating material, said tubular member having recesses inits opposite ends, the dimensions of said recesses being greater atpoints spaced from the ends of said tubular member, a resistor roddisposed within the bore 0! said member and having its end portionsdisposed within said recesses, metal in said recesses surrounding andembracing said end portions of said resistor rod and engaging the wallsof said recesses at said points, wire terminals embedded in the metal ofeach of said recesses, and an insulating substance sealing the endportions of said recesses.

4. In a device of the class described, in combination, a tubular memberformed from insulating material, said tubular member having recesses inits opposite ends, the dimensions of said recesses being greater atpoints spaced from the ends of said tubular member, a resistor roddisposed within the bore of said member and having its end portionsdisposed within said recesses, metal in said recesses surrounding andembracing said end portions of said resistor rod and engaging the wallsof said recesses at said points, and wire terminals having bent portionsembedded in said metal.

5. In a device of the class described, in combination, a tubular memberformed from insulating material having recesses formed in its oppositeends, the diameter of the inner portions of said recesses being greaterthan the diameter of said recesses at the ends thereof, a glass rodhaving a. carbonaceous substance coated thereon fitting within andsubstantially filling the bore of said tubular member and having endportions extending into said recesses, metal filling the portions ofsaid recesses having enlarged diameters and embracing said end portionsof said rod, and wire terminals embedded in said metal and extendingoutwardly therefrom substantially in axial directions with respect tosaid tubular member.

HAROLD FENDER.

